This is dirs_links/t_unlink.c (Listing 18-1, page 347), an example from the book, The Linux Programming Interface.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

This page shows the "distribution" or "book" version of the file (why are there two versions?), or the differences between the two versions. You can switch between the views using the tabs below.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.


Download dirs_links/t_unlink.c

  Cover of The Linux Programming Interface

Function list (Bold in this list means a function is not static)

#include <sys/stat.h>
#include <fcntl.h>
#include "tlpi_hdr.h"

#define CMD_SIZE 200
#define BUF_SIZE 1024
main(int argc, char *argv[])
    int fd, j, numBlocks;
    char shellCmd[CMD_SIZE];            /* Command to be passed to system() */
    char buf[BUF_SIZE];                 /* Random bytes to write to file */

    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s temp-file [num-1kB-blocks] \n", argv[0]);

    numBlocks = (argc > 2) ? getInt(argv[2], GN_GT_0, "num-1kB-blocks")
                           : 100000;

    fd = open(argv[1], O_WRONLY | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
    if (fd == -1)

    if (unlink(argv[1]) == -1)          /* Remove filename */

    for (j = 0; j < numBlocks; j++)     /* Write lots of junk to file */
        if (write(fd, buf, BUF_SIZE) != BUF_SIZE)
            fatal("partial/failed write");

    snprintf(shellCmd, CMD_SIZE, "df -k `dirname %s`", argv[1]);
    system(shellCmd);                   /* View space used in file system */

    if (close(fd) == -1)                /* File is now destroyed */
    printf("********** Closed file descriptor\n");

    system(shellCmd);                   /* Review space used in file system */


Download dirs_links/t_unlink.c

Note that, in most cases, the programs rendered in these web pages are not free standing: you'll typically also need a few other source files (mostly in the lib/ subdirectory) as well. Generally, it's easier to just download the entire source tarball and build the programs with make(1). By hovering your mouse over the various hyperlinked include files and function calls above, you can see which other source files this file depends on.

Valid XHTML 1.1